1. Field of the Invention
This invention pertains to the field of high power vacuum switches.
2. The Prior Art
A multiplicity of different contact geometry designs for vacuum switches is known. However, in the art so far only disc or pot-shaped contact designs have made any inroads (compare for example German Display Copies Nos. 1,210,933 and 1,196,751). Generally, the disc-shaped contact designs are more favorable costwise than the pot-shaped designs, because their machining is considerably simpler. Disc-shaped contacts have a central current feed and in the beveled edge of the disc some crescent-shaped slots are provided.
A considerable improvement of this proven contact geometry is described in the German Publication Copy No. 2,352,540. In these vacuum switch contacts both the central contact surfaces and the arc baffles have a separate current feed. The result is that in case of a migration of the arc contact points in a radial direction initially, the current forces removed from the center increase. However, forces acting in central direction occur when the contact points approach the edge of the switch parts. Thus no current forces can occur which expel the arcs from the area between the switch contacts. However, it is a disadvantage that switch contacts with this contact geometry can be produced with difficulty and the contacts become very costly. Moreover, the arc has a good opportunity to contract on the central current feed because of the low resistance of the contact bolts. Thus, contact erosions may be created which are undesirable on switch contact surfaces of vacuum switches. Moreover, gaps with sharp edges are undesirable at the most narrow point of the contact gap because of the high electric field strength developing at the edges at dielectric stress.